Label-Free Plasmonic Biosensor for Rapid, Quantitative, and Highly Sensitive COVID-19 Serology: Implementation and Clinical Validation (preprint)

Serological tests are essential for the control and management of COVID-19 pandemic, not only for current and historical diagnostics but especially for surveillance, epidemiological, and acquired immunity studies. Clinical COVID-19 serology is routinely performed by enzymatic or chemiluminescence immunoassays (i.e., ELISA or CLIA), which provide good sensitivities at the expense of relatively long turnaround times and specialized laboratory settings. Rapid serological tests, based on lateral flow assays, have also been developed and widely commercialized, but they suffer from limited reliability due to relatively low sensitivity and specificity. We have developed and validated a direct serological biosensor assay employing proprietary technology based on Surface Plasmon Resonance (SPR). The biosensor offers a rapid -less than 15 min- identification and quantification of SARS-CoV-2 antibodies directly in clinical samples, without the need of any signal amplification. The portable plasmonic biosensor device employs a custom-designed multi-antigen sensor biochip, combining the two main viral antigens (RBD peptide and N protein), for simultaneous detection of human antibodies targeting both antigens. The SPR serology assay reaches detection limits in the low ng mL-1 range employing polyclonal antibodies as standard, which are well below the commonly detected antibody levels in COVID-19 patients. The assay has also been implemented employing the first WHO approved anti-SARS-CoV-2 immunoglobulin standard. We have carried out a clinical validation with COVID-19 positive and negative samples (n=120) that demonstrates the excellent diagnostic sensitivity (99%) and specificity (100%). This positions our biosensor device as an accurate, robust, and easy-to-use diagnostics tool for rapid and reliable COVID-19 serology to be employed both at laboratory and decentralized settings for the management of COVID-19 patients and for the evaluation of immunological status during vaccination, treatment or in front of emerging variants.

Cytokine Hemoadsorption As Rescue Therapy for Critically Ill Patients with SARS-CoV-2 Pneumonia with Severe Respiratory Failure and Hypercytokinemia (preprint)

Background : A dysregulated inflammatory response, known as “cytokine storm”, plays an important role in the pathophysiology of coronavirus 2019 disease (COVID-19). There is a subgroup of patients who develop a hyperinflammatory response with severe respiratory failure and organ dysfunction with high mortality. Identifying these patients is outstanding as they could benefit from specific therapies, such as cytokine removal by hemoadsorption. Methods: Single-center, observational and prospective study of critically ill patients with SARS-CoV-2 pneumonia, severe acute respiratory failure and hypercytokinemia. All patients received cytokine hemoadsorption using Cytosorb® (Cytosorbents Europe, Berlin, Germany). The indication for treatment was acute respiratory failure, inadequate prone response, and hypercytokinemia. Results : A total of 343 patients were admitted to the ICU due to SARS-Cov-2 infection between March 3, 2020, to June 22, 2020. Of these, six patients [5 (83.3%) men; mean age 57 (10.5) years; SOFA 5 (1.4); mean Acute Physiology And Chronic Health Evaluation (APACHE) II score 19.5 (6)] underwent hemoadsorption with Cytosorb®. All patients fulfilled the Berlin criteria for severe acute respiratory distress syndrome (ARDS), underwent prone positioning, and were on mechanical ventilation for 15.2 (7.2) days. One session of 16 (9.0) hours duration was performed. IL-6 levels were significantly reduced [(pre- hemoadsorption levels 17.367 (4.539– 22.532) pg/ml; post-hemoadsorption levels 2.403 (917 – 3.724) pg/ml, p = 0.043], and improvements in oxygenation were observed [pre-hemoadsorption PaO 2 /FiO 2 ratio was 103 (18.4), post- hemoadsorption PaO2/FiO2 ratio was 222 (20.9), p = 0.029]. We documented the clinical improvement and rapid reversal of organ dysfunction [pre-hemoadsorption Sequential Organ Failure Assessment (SOFA) score 9 (4.7); post- hemoadsorption SOFA score 7.7 (5.4), p = 0.046]. Inflammatory markers (C-reactive protein, D-dimer, and ferritin) also improved significantly. Mean ICU stay was 17.2 (8.0) days. ICU and in-hospital mortality was 33.7%. Conclusions : In our cohort, patients with SARS-CoV-2 pneumonia and severe acute respiratory failure and hypercytokinemia who received cytokine hemoadsorption, an important reduction in IL-6 levels and improvements in oxygenation and SOFA score were observed.